What is a Credit Card Number?
A credit card number is the unique 15 to 19 digit number printed or embossed on the front of a payment card. It identifies the card issuer, the cardholder's account, and includes a check digit for validation. The full card number is classified as cardholder data under PCI DSS and must be protected whenever it is stored, processed, or transmitted.
What the Numbers Mean
A credit card number is not random. Each section carries specific information:
Issuer Identification Number (IIN/BIN)
The first six to eight digits identify the card network and issuing bank. This is also known as the Bank Identification Number (BIN). For example, Visa cards start with 4, Mastercard with 51-55 or 2221-2720, and American Express with 34 or 37.
Account Number
The digits between the BIN and the final check digit identify the cardholder's individual account. This section is unique to each card and links to the cardholder's account with the issuing bank.
Check Digit
The last digit is calculated using the Luhn algorithm. This mathematical formula validates whether the card number is structurally correct. It catches simple data entry errors — if someone mistypes a single digit, the Luhn check will fail and the number will be rejected before it reaches the payment processor.
Card Number Lengths
Different card networks use different number lengths:
- Visa: 16 digits (some older cards use 13)
- Mastercard: 16 digits
- American Express: 15 digits
- Discover: 16 digits
- Diners Club: 14 digits
How Card Numbers Are Used in Transactions
When you make a purchase, the card number is sent to the payment processor along with the expiry date and, for card-not-present transactions, the card security code (CVV/CVC). The processor uses the BIN to route the transaction to the correct issuing bank, which then checks the account number, available balance, and fraud indicators before approving or declining the payment.
Protecting Card Numbers
Under PCI DSS, the full card number (known as the Primary Account Number or PAN) is classified as sensitive cardholder data. Organisations that handle card numbers must:
- Encrypt them in storage and during transmission
- Restrict access to staff who need it
- Never store them in plain text in files, emails, or databases
- Mask the number when displaying it (showing only the last four digits)
- Maintain audit trails of all access to card data
The most effective way to reduce risk is to avoid handling card numbers entirely. Technologies like tokenisation replace the actual number with a non-sensitive token, and DTMF masking prevents card numbers from entering telephone systems during phone payments.
Paytia's platform is designed so that credit card numbers never enter your business systems. When a customer makes a phone payment, they key their card number on their phone keypad. Paytia's DTMF suppression technology prevents the tones from reaching the agent, and the card number is routed directly to the payment processor through Paytia's PCI DSS Level 1 certified infrastructure.
Your agents, call recordings, and business systems never see or store the credit card number. This removes the most sensitive piece of cardholder data from your environment entirely.
Frequently Asked Questions
How many digits are in a credit card number?
Most credit card numbers are 16 digits long (Visa, Mastercard, Discover). American Express cards have 15 digits, and Diners Club cards have 14. The length depends on the card network.
What do the first digits of a credit card number mean?
The first six to eight digits identify the card network and issuing bank. Visa cards start with 4, Mastercard with 51-55 or 2221-2720, and American Express with 34 or 37. This section is called the Bank Identification Number (BIN) or Issuer Identification Number (IIN).
Is it safe to give your credit card number over the phone?
Giving your card number verbally over the phone carries risk because the agent can hear it and call recordings may capture it. Secure phone payment solutions use DTMF masking, which lets you key your card number on your phone keypad while the agent stays on the line but cannot hear the digits. This is the safest way to pay by card over the phone.
See how Paytia handles credit card number
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